mathjs/lib/function/arithmetic/unary.js

module.exports = function (math) {
  var util = require('../../util/index.js'),

      Complex = require('../../type/Complex.js'),
      Unit = require('../../type/Unit.js'),
      collection = require('../../type/collection.js'),

      isNumBool = util.number.isNumBool,
      isComplex = Complex.isComplex,
      isUnit = Unit.isUnit,
      isCollection = collection.isCollection;

  /**
   * Inverse the sign of a value.
   *
   *     -x
   *     unary(x)
   *
   * For matrices, the function is evaluated element wise.
   *
   * @param  {Number | Boolean | Complex | Unit | Array | Matrix} x
   * @return {Number | Complex | Unit | Array | Matrix} res
   */
  math.unary = function unary(x) {
    if (arguments.length != 1) {
      throw new util.error.ArgumentsError('unary', arguments.length, 1);
    }

    if (isNumBool(x)) {
      return -x;
    }
    else if (isComplex(x)) {
      return new Complex(
          -x.re,
          -x.im
      );
    }
    else if (isUnit(x)) {
      var res = x.clone();
      res.value = -x.value;
      return res;
    }

    if (isCollection(x)) {
      return collection.deepMap(x, unary);
    }

    if (x.valueOf() !== x) {
      // fallback on the objects primitive value
      return unary(x.valueOf());
    }

    throw new util.error.UnsupportedTypeError('unary', x);
  };
};